A GGGGCC (G4C2) hexanucleotide repeat expansion (HRE) in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Recent studies support an HRE RNA gain-of-function mechanism of neurotoxicity, and we previously identified protein interactors for the G4C2 RNA including RanGAP1. A candidate-based genetic screen in Drosophila expressing 30 G4C2 repeats identified RanGAP (Drosophila ortholog of human RanGAP1), a key regulator of nucleocytoplasmic transport, as a potent suppressor of neurodegeneration. Enhancing nuclear import or suppressing nuclear export of proteins also suppresses neurodegeneration. RanGAP physically interacts with HRE RNA and is mislocalized in HRE-expressing flies, neurons from C9ORF72 ALS patient-derived induced pluripotent stem cells (iPSNs), and in C9ORF72 patient brain tissue. Nuclear import is impaired as a result of HRE expression in the fly model and in C9ORF72 iPSNs, and these deficits are rescued by small molecules and antisense oligonucleotides targeting the HRE G-quadruplexes. Nucleocytoplasmic transport defects may be a fundamental pathway for ALS and FTD amenable to pharmacotherapeutic intervention.

It has been hypothesized that α-synuclein (αS) misfolding may begin in peripheral nerves and spread to the central nervous system (CNS), leading to Parkinson disease and related disorders. Although recent data suggest that αS pathology can spread within the mouse brain, there is no direct evidence for spread of disease from a peripheral site. In the present study, we show that hind limb intramuscular (IM) injection of αS can induce pathology in the CNS in the human Ala53Thr (M83) and wild-type (M20) αS transgenic (Tg) mouse models. Within 2-3 mo after IM injection in αS homozygous M83 Tg mice and 3-4 mo for hemizygous M83 Tg mice, these animals developed a rapid, synchronized, and predictable induction of widespread CNS αS inclusion pathology, accompanied by astrogliosis, microgliosis, and debilitating motor impairments. In M20 Tg mice, starting at 4 mo after IM injection, we observed αS inclusion pathology in the spinal cord, but motor function remained intact. Transection of the sciatic nerve in the M83 Tg mice significantly delayed the appearance of CNS pathology and motor symptoms, demonstrating the involvement of retrograde transport in inducing αS CNS inclusion pathology. Outside of scrapie-mediated prion disease, to our knowledge, this findiing is the first evidence that an entire neurodegenerative proteinopathy associated with a robust, lethal motor phenotype can be initiated by peripheral inoculation with a pathogenic protein. Furthermore, this facile, synchronized rapid-onset model of α-synucleinopathy will be highly valuable in testing disease-modifying therapies and dissecting the mechanism(s) that drive αS-induced neurodegeneration.amyloid | Parkinson disease S ynucleinopathies are a group of diseases defined by the presence of amyloidogenic α-synuclein (αS) inclusions that can occur in neurons and glia of the central nervous system (CNS) (1-4). In Parkinson disease (PD), a causative role for αS has been established via the discovery of mutations in the αS gene SNCA resulting in autosomal-dominant PD (4-11). Although αS inclusions (e.g., Lewy bodies) are the hallmark pathology of PD, how they contribute to disease pathogenesis remains controversial (1,3,4,12).Postmortem studies have suggested that αS pathology may spread following neuroanatomical tracts (13-15) and between cells (16-18). αS pathology has also been found in the peripheral nervous system (PNS): for example, in the enteric and pelvic plexus (19,20). And it has been suggested that αS pathology might originate in the nerves of the PNS and spread to the CNS (14). Experimentally, it has been reported that intracerebral injections of preformed amyloidogenic αS fibrils in nontransgenic (nTg) and αS transgenic (Tg) mice induce the formation of intracellular αS inclusions that appear to progress from the site of injection (21-26). Collectively, these studies support the notion that αS inclusion pathology may propagate via a prion-like conformational self-templating mechanism (27, 28). A caveat of the direct intracerebral injection of αS is tha...

Mutations of the isocitrate dehydrogenase 1 and 2 genes (IDH1 and IDH2) are commonly found in primary brain cancers. We previously reported that a novel enzymatic activity of these mutations results in the production of the putative oncometabolite, R(–)-2-hydroxyglutarate (2-HG). Here we investigated the ability of magnetic resonance spectroscopy (MRS) to detect 2-HG production in order to non-invasively identify patients with IDH1 mutant brain tumors. Patients with intrinsic glial brain tumors (n = 27) underwent structural and spectroscopic magnetic resonance imaging prior to surgery. 2-HG levels from MRS data were quantified using LC-Model software, based upon a simulated spectrum obtained from a GAMMA library added to the existing prior knowledge database. The resected tumors were then analyzed for IDH1 mutational status by genomic DNA sequencing, Ki-67 proliferation index by immunohistochemistry, and concentrations of 2-HG and other metabolites by liquid chromatography–mass spectrometry (LC–MS). MRS detected elevated 2-HG levels in gliomas with IDH1 mutations compared to those with wild-type IDH1 (P = 0.003). The 2-HG levels measured in vivo with MRS were significantly correlated with those measured ex vivo from the corresponding tumor samples using LC–MS (r2 = 0.56; P = 0.0001). Compared with wild-type tumors, those with IDH1 mutations had elevated choline (P = 0.01) and decreased glutathione (P = 0.03) on MRS. Among the IDH1 mutated gliomas, quantitative 2-HG values were correlated with the Ki-67 proliferation index of the tumors (r2 = 0.59; P = 0.026). In conclusion, water-suppressed proton (1H) MRS provides a non-invasive measure of 2-HG in gliomas, and may serve as a potential biomarker for patients with IDH1 mutant brain tumors. In addition to 2-HG, alterations in several other metabolites measured by MRS correlate with IDH1 mutation status.

A two-dimensional (2D) chemical shift correlated MR spectroscopic (COSY) sequence integrated into a new volume localization technique (90°-180°-90°) is proposed for whole-body MR spectroscopy (MRS).Due to the recent improvements in the design of B 0 gradient and RF coils, 1 H MR spectra have been recorded in human brain with excellent water suppression using short TE, as short as 15 ms, and several cerebral metabolites have been identified (1-4). During the past decade alterations in several metabolites, namely, N-acetylaspartate (NAA), glutamate/glutamine (Glx), choline (Ch), creatine (Cr), myo-inositol (mI), and ␥-aminobutyrate (GABA) have been reported in different pathologic states involving the central nervous system (CNS) (5-10). Absolute quantitation of cerebral metabolites in vivo has also been reported for only a few metabolites, albeit with limited success (11-13). Due to severe overlap of these metabolites, an unambiguous assignment of J-coupled metabolite multiplets is severely hindered at 1.5 T field strength.One-dimensional (1D) MR spectral editing techniques to unravel the overlapping resonances rely on J-coupled proton metabolites that have well-separated multiplets. A technique based on subtraction methodology is very sensitive to motion artifacts leading to subtraction errors. An additional drawback is that only one metabolite can be identified at a time. Successful attempts in editing GABA and glutamate using whole-body MRI/MRS scanners have been presented by other researchers (13,14). Single-shotbased multiple-quantum filtered MR spectroscopic sequences have also been implemented on whole-body scanners, but a severe signal loss associated with various coherence transfer pathways made it less attractive to human applications (15)(16)(17).A localized version of a two-dimensional (2D) J-resolved MR spectroscopic (JPRESS) sequence using the PRESS sequence for volume localization was recently proposed (18 -20). Even though the JPRESS sequence retains 100% of the magnetization from a localized volume of interest (VOI), the strong coupling effect inherent at 1.5 T field strength resulted in a complex 2D cross-peak pattern for NAA, glutamate/glutamine, GABA, and other cerebral metabolites (19). Also, some of the 2D cross-peaks were heavily T 2 -weighted during the long incremental delays necessitated by the second dimension of the JPRESS spectrum. An oversampled J-resolved sequence has also been proposed recently (21).Compared to the 2D J-resolved spectra, a COSY spectrum produces a better dispersion of J-cross-peaks, although it requires a larger spectral window to be sampled during the evolution period (22). Different versions of the localized COSY sequence have been implemented by other researchers (23-33). McKinnon and Bosiger (23) proposed a conventional COSY sequence with hard RF pulses (90°-t 1 -90°) followed by three volume selective 180°RF pulses. Haase et al. (24) implemented a COSY combined with an outer volume suppressing sequence, namely, LOCUS. Many previous attempts to develop localiz...